BATH — A fire Thursday afternoon at the Family Focus day care center has been ruled arson, police said Friday.

Firefighters responded at about 4:20 p.m. to 2 Davenport Circle — the former Bath Memorial Hospital building — where smoke was coming from the day care off Winship Street, Bath Police Lt. Robert Savary said.

Internal sprinklers had extinguished the fire, which caused “minimal damage,” he said.

The fire damage was contained to a single room, according Sgt. Ken Grimes of the state fire marshal’s office, but water damaged other parts of the building.

Savary said a broken window indicated the perpetrator had entered the building through a window with an air conditioner, spread accelerant and then fled the scene.

The Maine State Fire Marshal’s office responded and the case is under investigation by the state fire marshal and Bath police.

Savary wasn’t sure whether Family Focus could resume operations.

“It’s a lucky thing the sprinklers put the fire out,” he said. “It could have been really bad.”

A phone call to Family Focus was not immediately returned Friday.